The Declaration of Independence, adopted on July 4, 1776, declared the colonies' independence from Britain. It remains a foundational document in United States history.

The American Civil War, fought from 1861 to 1865, was primarily a conflict over slavery and states' rights. Its outcomes reshaped the nation politically and socially.

Thomas Jefferson is recognized as the primary author of the Declaration of Independence. His writing eloquently outlined the colonies' grievances and right to seek independence.

The United States Constitution, ratified in 1788, lays out the framework for the federal government and guarantees certain rights to its citizens. It remains central to the nation's legal and political systems.

Westward Expansion was characterized by the belief in Manifest Destiny and involved significant territorial growth, often resulting in conflicts with Native American tribes. It played an influential role in shaping the nation's early identity.

Reconstruction aimed to rebuild the war-torn South and integrate freed slaves into American society. The era was marked by efforts to redefine civil rights and rebuild political structures.

Plessy v. Ferguson, decided in 1896, established the 'separate but equal' doctrine, which legitimized racial segregation for many decades. This decision had a profound impact on race relations in the United States.

Theodore Roosevelt's domestic policies were centered on regulating large corporations and breaking up monopolies to ensure fair competition. His progressive reforms reshaped economic practices in the United States.

The Stock Market Crash of 1929 is widely recognized as the trigger for the Great Depression. The economic crash led to severe financial instability and widespread unemployment.

The New Deal introduced a series of programs designed to offer immediate relief and foster long-term recovery from the Great Depression. Its legacy includes a redefined role of the federal government in economic affairs.

Ratified in 1870, the 15th Amendment prohibited denying the right to vote on the basis of race, color, or previous condition of servitude. This amendment was a major milestone in expanding democratic participation.

The Korean War is considered a 'proxy war' because it involved indirect conflict between the superpowers during the Cold War. Major powers supported opposing sides without engaging in direct combat.

The Civil Rights Movement sought to dismantle legalized racial discrimination and segregation. Its efforts led to significant changes in laws and societal norms regarding equality.

The Brown v. Board of Education decision in 1954 ruled that segregated schools are inherently unequal. This landmark ruling paved the way for the desegregation of public schools and other institutions.

The attack on Pearl Harbor in 1941 was a decisive moment that led the United States to enter World War II. This event fundamentally shifted U.S. foreign policy towards greater international military engagement.

Manifest Destiny was a belief that American expansion across the continent was both justified and inevitable. This ideology underpinned many policies that resulted in territorial growth and influenced the nation's self-perception.

During the 1920s, the Federal Reserve's loose monetary policies are considered a contributing factor to the speculative bubbles in the economy. When these bubbles burst, they helped trigger the economic collapse known as the Great Depression.

The New Deal redefined the federal government's relationship with the economy by significantly increasing its regulatory and welfare roles. Its long-term effects are evident in the modern American welfare system and ongoing government intervention in economic matters.

Cold War tensions led to a domestic atmosphere of fear and suspicion, notably manifesting in McCarthyism. This period saw heightened governmental surveillance and restrictions on civil liberties, influenced by the perceived threat of communism.

Social movements in the latter half of the 20th century played a pivotal role in prompting policy reforms. Their grassroots activism and advocacy efforts led to transformative changes in civil rights, environmental policies, and gender equality.